The study revealed that germ-free (GF) mice are more susceptible to infection with Listeria monocytogenes than mice with conventional (CV) intestinal microbiota.
24 hours after infection, germ-free mice harbored 10,000 times more L. monocytogenes bacteria in their small intestines and about 1,000 times more Listeria in their mesenteric lymph nodes than the conventional mice.
The study showed that the microbiota interferes with the microRNA response upon oral Listeria infection and identify protein-coding target genes whose expression correlates with the miRNA.
Lack of defence?
“The higher susceptibility of the GF mice to bacterial infection has been proposed to be due to a lack of host immune defense,” said the researchers.
“We hypothesized that this lower efficiency to mount a proficient defense might correlate with a different miRNA expression, leading to the host failure to adapt its gene transcriptomic response to infection.”
L. monocytogenes is a gram-positive pathogen that crosses the intestinal barrier to reach the lymph and the bloodstream, allowing the bacterium to disseminate.
The researchers investigated the role of the intestinal microbiota in the regulation of host protein-coding genes and microRNA (miRNA or miR) expression during Listeriainfection.
They showed that expression of five intestinal microRNA (miRNA) molecules decreases in conventional mice upon Listeria infection while it did not in germ-free mice.
This indicates that the gut microbiota may determine how the mouse genome expression is reprogrammed in the gut and how it responds to an infection.
Six miRNAs whose expression decreased upon Listeria infection in conventional mice were identified and five expressed variations dependent on the presence of the microbiota.
miRNA role
Few studies have addressed the impact microbiota has on miRNA expression during bacterial infections.
Pascale Cossart of the Institut Pasteur in Paris said that the study and others indicate that miRNA may be involved in protecting the host from infection, but their precise role isn't yet clear.
At miRNA level the differences were not evident the most highly expressed miRNAs were produced at the same levels in both types of mice and they didn't change much after infection.
Source: American Society for Microbiology
“The Intestinal Microbiota Interferes with the microRNA Response upon Oral Listeria Infection”
Authors: Cristel Archambaud, Odile Sismeiro, Joern Toedling, Guillaume Soubigou, Christophe Bécavin, Pierre Lechat, Alice Lebreton, Constance Ciaudo, Pascale Cossart